1. Field of the Invention
The present invention relates to an electromagnetic shielding method for electronic components disposed on printed wiring boards and an electromagnetic shielding film used in the method.
2. Description of the Related Art
In order to prevent electromagnetic wave mutual interference of electronic parts disposed on printed wiring boards, can shields using metal thin plates are used. An example of the can shields is as follows.
First, a conductive frame member including a conductive metal thin plate is formed, using a mold, in a fence-like (wall-like) frame shape which has a constant height and surrounds a portion to be electromagnetically shielded on a printed wiring board. The conductive frame member is provided on the printed wiring board so as to surround the portion to be electromagnetically shielded. In this case, the conductive frame member is electrically grounded by soldering to a grounding conductor of the printed wiring board.
In addition, apart from the conductive frame member, a cover member made of a conductive metal thin plate is formed, using a mold, in a shape corresponding to the frame shape that surrounds the portion to be electromagnetically shielded on the printing wiring board so that the cover member is fitted to the conductive frame member. The cover member is fitted to the frame member provided on the printed wiring board. As a result, a can shield is formed to surround, by a conductor, the portion to be electromagnetically shielded on the printing wiring board.
Another example of the can shield uses a conductive case member formed by integrating the frame member and the cover member each including a conductive metal thin plate. In this example, the case member having an open side and made of a metal thin plate is formed using a mold. The conductive case member is disposed to cover a portion to be electromagnetically shielded so that the open side faces the printed wiring board. Then, the conductive case member and a grounding conductor of the printed wiring board are bonded to each other by soldering.